Dibutyl hydrogen thiophosphate amine salt is an anti-wear product that has been produced by Ethyl Corporation for use in crankcase products. This product is also prepared for gear packages by the in-situ reaction of dibutyl hydrogen phosphite (DBHP), sulfurized isobutylene (SIB) and an amine to form the thiophosphate amine salt. To improve the thermal stability of gear lubricant packages, tertiary-butyl polysulfide (an extreme pressure additive) has been substituted for sulfurized isobutylene. When the above reaction takes place in the presence of t-butyl polysulfide, a strong mercaptan odor is generated in the final product that is attributable to the reduction of unstable sulfur--sulfur bonds in the polysulfide. A low odor, thermally stable formulation for gear packages that contains polysulfides would be an advancement in the art.